1. Field of the Invention
The present invention relates to a substrate transfer module and substrate processing system, and more particularly to a substrate transfer module which includes a substrate transfer device for transferring a substrate.
2. Description of the Related Art
Substrate processing systems for implementing desired processing on substrates which are wafers for semiconductor devices (hereinafter simply referred to as “wafers”) are well-known. One such substrate processing system includes a processing module which houses wafers and implements desired processing on the housed wafers, a load-lock module which is connected to the processing module and introduces and extracts wafers to and from the processing module, and a loader module (a substrate transfer module) which transfers wafers between a FOUP (Front Opening Unified Pod) housing a plurality of wafers and the load-lock module.
In the substrate processing system, the loader module includes a transfer chamber for housing the wafers. The processing module, the load-lock module and the transfer chamber of the loader module are connected together in the stated order. Although an interior of the processing module is maintained under near vacuum state, the pressure in an interior of the load-lock module can be switched between atmospheric pressure and near vacuum state. The pressure in the transfer chamber of the loader module is therefore maintained under at approximately atmospheric pressure.
The wafer transfer in the loader module is performed by a transfer arm provided in the transfer chamber. In the transfer chamber of the loader module, a unidirectional flow (a downward flow for instance) is produced by a fan filter unit provided in the loader module. The fan filter unit introduces an external atmosphere into the transfer chamber of the loader module, while removing debris from the external atmosphere using a built-in filter. This arrangement serves to prevent the introduction of debris which could cause occurrence of particles in the transfer chamber of the loader module.
In recent years, in response to demand for a way of reliably preventing attachment of particles, in particular, to the wafer, a dust-protection cover which is attached to the transfer arm and covers the upper-side of the wafer held by the transfer arm (see Japanese Laid-Open Patent Publication (Kokai) No. 2002-100786, for instance) has been developed.
However, in recent years types of the processing implemented on the substrate have been diversified, and corrosive gases (such as bromine gas, chlorine gas and fluorine gas) have come into use as a processing gas. When used, the corrosive gas can condense or solidify on the wafer which has undergone the processing in the processing module, and evaporate (to form outgas) after the wafer has been transferred to the loader module. The above-described dust-protection cover covers only the upper side of the wafer. This arrangement therefore has a shortcoming in that the components in the loader module corrode because the cover is unable to prevent the diffusion of the evaporated corrosive gas.
In recent years the grooves and the like formed in the wafer by etching have become finer. As a result, protection against finer particles (e.g. particles of a few tens of nm) is required. However, the fan filter unit is unable to remove particles of a few tens of nm. Since the transfer arm enters the load-lock module adjacent to the processing module, reaction products generated from the processing gas sometimes adhere to the transfer arm. These reaction products peel off in the transfer chamber of the loader module to form particles. Moreover, contacting portions of the transfer arm, for instance, parts of the pick may separate as a result of contact with the wafer, and form particles. That is, there are in the transfer chamber a large number of particles which require removal. Since the volume of the transfer chamber is large, it is difficult to remove all of the particles therein. Also, the above-describe dust-protection cover alone is not capable of reliably preventing particles from adhering to the wafer.
In the future, the diameter of wafers is set to increase further (to φ450 mm for instance), and there will be a corresponding increase in the size of the transfer chamber of the loader module. Since this will bring about a corresponding increase in the volume of the transfer chamber from which debris is to be removed, improvements in the functionality of the loader module, for instance, improvements in the processing capability of the fan filter unit to maintain the debris removing capability, are required. Since these increases will bring about increases in the size of the loader module components, there is a risk that the manufacturing cost and size of the loader module will increase.